The proposed research involves the study of the amphipathic helix, a presumed lipid-associating domain of plasma apolipoproteins, using synthetic oligopeptides. Sequences of the model amphipathic peptides are based on a generalized model for an amphipathic helix as well as upon native apolipoprotein sequences. The ability of the amphipathic model peptides to interact with lipid has been established through a series of physical studies. In addition, analog peptides have been prepared which have assisted in determining characteristic properties, significant to the lipid binding ability of the amphipathic peptides. In the report, the importance of the position and number of changed residues along the polar face of the helix has been investigated. The critical length of an amphipathic helix will be established in future studies by the use of variable length synthetic peptides. This study will help evaluate the amphipathic helix hypothesis for lipid associating plasma apolipoproteins. Significant properties of the amphipathic helix model will be identified so that more effective and useful models for the study of some aspects of the mechanism of action of plasma apolipoproteins can be designed.